Obeserving bacteris and blood


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There were two major goals of the “Observing Bacteria and Blood” experiment. The first was to establish a familiarity with the proper techniques for using a microscope. The experiment focused on both the basic components of a microscope (i.e. how to adjust the knobs and levers for the desired result) as well as how do decide the proper objective to use for observing a specimen. The second goal major goal of this experiment was to practice observing live specimens (yogurt and blood).


Exercise 1: Observation of prepared slides using the microscope. The observation of the 8 prepared slides was performed by making adjustments to the microscope (focus, condenser, light) in order to establish a clear image of the specimen. The slide was viewed through the 10x, 40x, and 100x objectives and all observations were recorded in the tables below.

Exercise 2&3: Observationof yogurt and blood. The yogurt and blood slides were prepared as described in the Labpaq manual. The slides were observed using the 10x, 40x, and 100x objectives and all observations were recorded in the tables below.


Exercise 1
Part 1Part 2
150x600x1500x (Oil Immersion)
Amoeba proteus


Ascaris Eggs

“e” slide


Penicillium w/conidia


Yogurt bacteria

Exercise 2 & 3
Ex 2:
Fresh Yogurt
Ex 3:
Blood Smear

Photos/Drawings: (Insert and label images here. If image file (JPEG or GIF) sizes are too large they may be uploaded separately.)

Analysis/Interpretation: Based on the observations detailed above, it can be concluded that the microscope is a powerful tool in the observation of organisms that are small in size. It was important to have a number of objectives of different magnifying power in order to be able to discern the level of magnification needed to best study a sample. In addition, the examination of the yogurt sample allowed for the observation of the varying shapes and arrangement of bacterial cells. The use of a microscope to observe the blood smear highlighted the many important components of human blood that are not evident by the naked eye.

Application: In performing this experiment I have learned many important aspects of microbiology that apply to healthcare. First, there is plenty of information that can be discovered by looking at a sample under the microscope … size, arrangement, number of organism. For example, this information can be utilized in making an initial identification on a patient sample in a hospital laboratory. Second, some microorganisms can be beneficial such as those bacteria that can be cultured from yogurt. Furthermore, these microorganisms can also be used to build back a healthy population of intestinal bacteria in patients who have recently been taking antibiotics.

Answers to the LabPaq Questions

1) Questions A. Identifythe following parts of the microscope and describe the functionof each.

a. Ocular- eyepiece transmits and magnifies the image form the objective lens to the eye.

b.Body/tube-holds the eyepiece at proper distance from the objective lens and blocks light.

c.Nosepiece- rotating mount that hold objective lens.

d.Objective Lens- gathers light for the specimen.

e.Mechanical Stage- holds the specimen.

f.Apeture diaphragm control/disc- alters the amount of light that reaches the condenser. g.Lamp- produces the light.

h.Coarse focus knob-brings objects into focal point of the objective lens.

i.Fine focus knob- makes fine adjustments to focus the image.

j.Arm-holds all of the optical parts at a distance and aligns them.

k.Clips-hold the specimen still on the stage.

l.Base- supports the weight of all the microscope parts.

Define the following microscopy terms:

Focus: positions the objective lens at the proper distance from the specimen.

Resolution: Ability for the lens to show fine details of the object being observed.

Contrast: The darkness of the back ground relative to the specimen.

B. What is the purpose of immersion oil? To direct the light from the microscope directly to the slide and stop it from refracting. It creats a finer resolution and brightness.

Exercise 2: Observing Bacteria Cultures in Yogurt Questions A. Describe your observations of the fresh yogurt slide.

B. Were there observable differences between your fresh yogurt slide and the prepared yogurt slide? If so, explain.

C. Describe the four main bacterial shapes.

Cocci – oval or spherical shaped. Bacillus – are rod shaped. Spirillum – are thick, rigid spirals. Vibrio – are curved or a comma shaped rod.

D. What are the common arrangements of bacteria? Diplo – oval shaped, found in pairs.

Strepto – are cocci that arange into chains. Staphylo – are cocci that are arranged into irregular clusters, similar to grapes.

E. Were you able to identify specific bacterial morphologies on either yogurt slide? If so, which types?

Exercise 3: Preparing andObservingaBloodSlide Questions
A. Describe the cells you were able to see in the blood smear.

B. Are the cells you observed in your blood smear different than the bacterial cells you have observed? Why or why not?

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